Apparatus for recording and reproducing sound



Jan.2, 1940. J H T.ELA ND 2,185,933

APPARATUS FOR RECORDING AND REPRODUCING souNn Filed Dec. 1, 1937 2 Sheets-Sheet 1 Irv/617%; 79 $31404 1940- J. H. TIELAND 2,185,933

APPARATUS FOR RECORDING AND REPRODUCING SOUND Filed Dec. 1', 193'! 2 Sheets-Sheet 2 .17? are)? 24/ Patented Jan. 2, 1940 um 'rso STATES roa RECORDING AND nnrnonucme scum:

APPARATUS Johannes Hendrik Tleland, Utrecht, Netherlands Application December 1, 1937, Serial No. 177,821

- .In the Netherlands December I, 1936 4 Claims.

The present invention relates to apparatus for recording and reproducing sound and more particularly pertains to driving means for the turntables of such apparatus.

The duration of the playing time of the known gramophone records is rather restricted and it is determined by three factors-namely, the diameter of the record, the number of grooves per inch and the number of revolutions per 10 minute of the record.

With records having a diameter of 40 centimetres, a number of 125 grooves per inch and a number of revolutions of 78 per minute, provide a good quality of the sound 'and a duration 15; of the playing time of! minutes for each sideof the record may be attained. Of course the velocity of the groove, with respect of the picksecond. Consequently this velocity should be 817- tained in the inner sound grooves. In the grooves which are tnearer to the edge the velocity ina creases, so that the duration of the playing time is reduced.

An object of the invention is to increase the duration of the playing time and the invention is based on the idea that the velocity of rotation of the record during the cutting or -the reproducing operation is changed according to a deflnite law in such a manner that the instantaneous velocity of the pick-up with respect to-the groove is constant all over the surface of the record.

With a velocity of 50 centimetres per second 3000 cms. per minute are cut. The total length of the groove of a record having a diameter of 40 cms. and 750 grooves is 56,520 cms., so that the total duration of the playing time is increased to 18.8 minutes per side of the record or to 37.6 minutes per record, if the velocity of 50 cms. per second is maintained all over the surface ofthe record. Y

If special electrical-pick-ups are a plied and 45 correctedampliflers are used the cutting and the reproduction velocity can be reduced to 30 cms. ,per second and the number of. grooves can be increased to 150 per .inch. In that case, when the invention is applied, the total duration of the playing time will be over '78 minutes.

Other and'further features of the invention will be more apparent to those skilled in the art upon a consideration of the annexed drawings and the following description wherein an exemplary embodiment of the invention is disclosed.

' In the drawings Fig. 1 is a sectional elevational view she the general organization of the elements of the apparatus.

Fig. 2 is a. plan view of the apparatus.

Fig. 3 is an elevational view of part of the needle or pick-up support.

The device according to the invention is based on the idea that the speed ,of the turntable should be decreased, followingla'certain law, when the pick-up moves towards the outer edge of the record. x

The device. is driven by an electric'motor i V of suflicient power, having a constant speed. To

this end a squirrel cage motor with an auxiliary starter winding is very suitable. The motor I drives a gear 8 formed on the housing of a differential gear 4 by means of a worm 2.

The spindle I! of the differential gear carries no gear wheels 6 and I, meshing with gear wheels 8 and 9 of the two side-spindles l0, H. In case of equal load the difierential gear may be "con-1 sidered a unit and consequently the spindles I0] and II will havethe same speed as the diiieren- '25 tial sear. 1

The differential gear is supported on the frame in ball bearings l2, l3, whereas the spindle I0 is supported by ball bearings H, I! and thespindle H by ball bearings i8, ll.

The two side spindles l0, II are provided near their free ends with worms i8 and i9 respective- 1y, co-operating with wormwhe'els 20, ii.

The worm wheel ii is mounted on a vertical spindle 22 which is connectedby a still. rubber coupling 23 to the spindle 24 of the turntable 25. The weight of the turntable is supported on a bushing 44 having a conically shaped exterior surface which is wedged in the upper bearing of the spindle 24 to provides. brake action for the turntable. The friction provided by the bushing 44 is suflicient for preventing the turntable to rotate-freely so that the brake news hereinafter described will be more positive in controlling speed of the sound record. I

The vertical spindle '26, which is arranged at the right hand sideof Fig. 1, is provided with a governor with springs and centrifugal weights 21 said governor being provided with a regulating disc 28 with a curved active upper face. The curvature is such that it controls the change of speed of the turntable in such a way that a constant cuttingand Playing-velocity is obtained all over the record, and that theangular velocity is varied in accordance'with the instantaneous distance between the pick-up and the turntable spindle, as will be described hereinafter.

'The spindle 24 is also provided with a heavy flywheel 45, which guarantees a smooth motion.

Drioing mechanism of the pick-up The radial displacement of. the pick-up should vary in dependence of the variation of the velocity of the turntable. To this end a pick-up support 29 is arranged to move with a block 24 along two parallel rods 4i and 42.

These rods are attached to the' frame and between whicha threaded spindle 24 is arranged.

The transmission between the block 44 and the Thegovernor is driven by means of a rack gear 38 attached to the block 30 of the pick-up support 29 and supported in the frame in such a way that it is easily movable, so that the rack gear is moved together with the pick-up. The rack gear 28 drives a. pinion 24 having a diameter of approximately 6 centimetres. This pinion is mounted on a vertical spindle 44, hearing a smallerpinion 4i having a diameter of approximately 2 cms. which is in engagement with rack gear teeth of bar 42. The bar 42 is provided with a regulating member 42, such as a piece of raw hide, co-operating with the curved v upper face of the regulating disc 24. Whenthe upper rack gear moves a distance of item,

the lower bar 42 is displaced over a distance of 5 cms., so that the force exerted on the, governor becomes. almost three times as high and said governor is controlled very slowly and smoothly. The apparatus is designed'to maintain. a eon-' stant speed of the turntable with respect'to the needle or pick up device. If therecordlng' or provided by the gear wheels 34 and 4! will move the bar 42 at a speed which'is one-third-of the movement of the rack gear 44.. 'Iheouter displacement of the raw hide element 44' will de crease the frictional engagement thereof with the disk 24 and the speed of the shaft 24 will thus increase.

The increase in speed of theahaft 24 will remove part of the load from the spindle i4 and the rotation of the shaft Ii which drives the turntable 26 will decrease by reason of the differential gear mechanism arranged between the shafts l4 and II. The curvature of the upper face of the disc 24 is such that the angular velocity of the turntable decreases in a ratio which is inversely proportional to the length of the groove of the sound record.

If the sound record is cuter the sound is reproduced from grooves therein starting from aromas g the outer periphery the angular velocity of the shaft 24 should increase'asthe pick-up-support 24 moves towards the center of thesou'nd record.

While the invention has been described with reference to specific constructional details it is l made without departing from the spirit and scope of theinvention as set forth in the appended claims. i

, constant speed motor wherein the speed of rotation is dependent on the radial travel of a needle 1 over the turntable so as to provide constant linear speed for recording and reproduction, a differential gear driven by the motor, a shaft driven by the differential gear, a turntable spindle coupled to said shaft, another shaft 2 driven by the differential gear, and means associated with said last mentioned shaft operable to exert a brake action on the second shaft in accordance with the radial position of the needle with respect to the turntable. 2

2. In a device for driving the turntable of 'a sound reproduoing'and recording device by a constant speed motor whereinthe speed of rotation is dependent upon the radial travel of a needle over the turntable so as to provide con-' 3 stant linear speed for recording and reproducetion, a differential gear driven by the motor, a

shaft driven by the diflerential gear, a turntable spindle -coupled to said shaft, means exerting a constant braking action on said spindle, a another shaft driven by the differential gear,

and means associated with said last mentioned shaft operableto exert a braking action on the second shaft in accordance with the radial position of the needle with'respect to the tumtable. a

3. In a device for driving the turntable of a sound recording and. reproducing device by a constant speed motor wherein the speed of rotation is dependent on the radial travel of a needle over the turntable so as to provide constant linear speed for recording-and reproduction, a differential gear driven by .the motor, a shaft driven by the differential gear, a turntable spindle coupled to said shaft, another maft driven by the differential gear, a disc carried by the last mentioned shaft, brake means moved by the radial travel of the needle frictionaily engaging said disc. to exert a braking action thereon in accordance with the radial position of a needle with respect to the turntable.

4. adevice for driving the turntable of a soun recording and" reproducing deviceby a constant speed motor wherein the speed of rotation is dependent on the radial travel of a needle m ovcr the turntable soas to provide constant linear for recording and reproduction, a

diflerentiai 'gear driven by the motor, a shaft driven by the differential gear, a turntable spindie coupled to said shaft, another shaft driven a day the differential gear, a disc carried by the last mentioned shaft having a curved face, means frictionally engaging saidcurved face, and means for" moving said first mentioned means radially with respectv to said disc in acoordance with the radial travel of the needle with to the turntable.

JOBANNES HENDRIX TIE-AND. 

